Extraction of metals from their ores



UNITED STAT Es PATENT oi-"Fics.

EDWARD M. HAMILTON, OF SAN FRANCISCO, CALIFORNIA, ASSIG-NOR I'O HAMILTON, IBEAUCI-IAMP, WOODWORTI-I, INCORPORATED, OF SAN FRANCISCO, CALIFORNIA, A

CORPORATION OF CALIFORNIA.

EXTRACTION OF METALS FROM THEIR ORES.

Io Drawing. Original application filed March 14, 1917, Serial No. 154,848. Divided and this applica- Specification of Letters I Patent.

, Patented Dec. 6, 1921.

tion filed June 7, 1917. Serial No. 173,308.

To all whom it may concern:

Be it known that I, EDWARD M. HAMIL- TON, a subject of the King of Great Britain, residing at the city and county of San Francisco and State of California, have invented new and useful Improvements in the EX- traction of Metals from Their .Ores, of which the following is a specification.

This invention relates-to the recovery of certain metals from their ores and concentrates and pertains especially to a method for the extraction of molybdenum.

The usual method of dealing with molybdenum ores is in the case of the sulfid to roast and extract the oXid with ammonia, the resulting liquor being evaporated to dryness resulting in ammonium molybdate.

In the case of the ore wulfenite P'bMoO a hi h grade concentrate is first made and this concentrate is fused with soda ash gormin lead-carbonate and sodium niolybate. dissolved out and the liquor evaporated or molybdic acid may be precipitated by addition of 'an acid'to the liquor but this method is not satisfactory becauseprecipgitation is usually incomplete and the least excess of acid tends to redissolve the precipitate already formed.

It happens in the case of certain ores that it is impossible to obtain a concentrate high in 'molybdenum, and at the same time make a high percentage recovery of the metal in question from the ore; for instance, where molybdenum occurs in small quantities in ore containing a large proportion of sulfid's of iron. together with copper, gold and other heavy minerals, it is possible to recover by mechanical means as high as 90% of the molybdenum together With most of the heavy sulfide present resulting in a concentrate containing only a few per cent. (say from 1 to 10 per cent.) of molybdenum, the remainder belng almost entirely sulfids or other heavy minerals. Such a product is unsuitable for treatment to recover the molybdenum by any of the commercial methods now in use on the ground of expense. On the'other hand, if it is desired to make a concentrate containinga high perhe latter being soluble in water is centage of molybdenum (say from 10% to 50%) suitable for the present commercial processes of molybdenum recovery, the loss of molybdenum in the process of concentration is so high as to constitute a serious source of loss of the metal.

In addition to the above difficulties the presence of copper renders the ammonia process inapplicable since the copper being soluble in the ammonia is extracted with the molybdenum and it is'found very diflicult'to separate it.

The object of the present invention is to devlse a process whereby a concentrate-high 1n heavy minerals and containing a low molybdenum content such as that already described, can be treated successfully and at an expense within the limits demanded for a commercial process.

Preparation of the ore for treatment.- My process consists of first grinding the ma terial to be treated to a suitable degree of fineness or otherwise preparing it so that it becomes amenable to the sub-sequent reactions by chemical treatment necessary. In the case of molybdenum, except Where the same occurs as sulfids, I usually grind the ore to pass a 200 mesh standard sieve, although it may not be necessary in every case to grind as fine as this. Where the ore is in the form of a sulfid, as is commonly the case with molybdenum ores, it may be necessary to roast the ore. Where the ore is to be roasted it is only necessary ordinarily to grind the sulfid ore to about 20 mesh in which size it yields readily to treatment and generally requires no further grinding after roasting. I have found it advisable in the case of a roasted ore to give a thorough water-wash to remove soluble salts of copper and iron before proceeding to digest the pulp in the soda solution.

Such a washing may be done either by percolation or by agitation, the pulp in the latter case being of course filtered before Molybdem'te (after roasting) Ratio of s0Zutz'0n.The ratio of solution. to ore in the mixture is not vital to the reaction but with low grade material it is advisable to keep it low, say between 1: 1 and 2:1, both to reduce the quantity of liquor to be handled subsequently and also to obtain a higher degree of concentration of the dissolving reagent,-but in the treatment of products rich in molybdenum it is usually better to increase the dilution since otherwise there may be a formation of large crystals of sodium molybdate which may be troublesome to dissolve during the washing out process.

Heating-The pulp so formed is heated up to or above the boiling point of the solution.

In the case of molybdenite when the or? is roasted to oxid the reaction-usually takes place rapidly and completely at the atmospheric boiling point so in most caseslI do not find it necessary to raise the temperature above that point. In treating wulfenite, however, the higher temperature obtained by heating under pressure is of great assistance.

The higher the temperature rises above the atmospheric boiling point ofwater the more rapid and complete is the reaction, and I find a useful point to work at is one 50 hundred (100) pounds pressure within the Receptacle equal to a temperature of 327.9 degrees F. When this temperature has been maintained long enough to complete the reaction, which may take from one to three hours the pressure is lowered and the charge withdrawn, or what is preferable for a working plant a series of such receptacles maybe used, so arranged that the pulp is pumped from one to the other and continu-- ously discharges at the end of the series, the

speed of fiow being determined by the time 1t is found necessary to keep the ore under the influence of the heat and reagent.

Filtering and -washz'nglThe pulp after being subjected to the heating process i filtered and the residue well washed with water, the resulting liquor containing the molybdenum in the form of sodium molybdate.

I-treat the sodium molybdate with a solution of a salt of a metal, preferably a ferric salt, which precipitates the molybdenum as a double oxid of iron and molybdenum.

NeutraZz'zing.Before treating the molybdate solution with the iron solution I find it advantageous first to neutralize'with an acld any free'sodium carbonate that may be presmolybdenum is -no drawback when this metal is to be used for the manufacture of special steels as it is customary to add such ingredients in the form of ferro-alloys of the said metal. The precipitate obtained by my process after being dried and pulverized may be reduced to a ferro-alloy powder by igniting with carbon or to a ferro-alloy pig by fusion with carbon in the electric furnace, in either of which forms it is suitable I for addition to steel in the manufacture of special steels.

' To sum up the advantages of my process:

(1) It is applicable to products of concentration low in molybdenum such as it is unavoidable to make in many instances if a high recovery is to be obtained from the ore, and such as could not be profitably treated by processes at present in use.

(2) It solves the problem of the association of copper with molybdenum ore.

(3) It provides an eflicient and inexpensive method of recovering molybdenum from its alkaline solutions.

This application is a divison of my ori inal application, filed March 14, 1917, Serial ma eri l th Water and with a non=vo1ati1e 180 of recovering molybalkali-metal compound the aqueous solution of which is alkaline to form a pulp, heating the pulp to convert the molybdenum into a soluble compound, filtering, and recovering the values from the filtrate.

2. The process of recovering molybedenum from its molybdate ores and concentrates which comprises reducing the ore or concentrate to a suitable condition of fineness for further chemical treatment, mixing the pulverized material with Water and with suitable condition of fineness for further chemical treatment, mixing the pulverized material with water and with sodium carbonate to form a pulp, heating the ulp to convert the molybdenum into a solub e compound, filtering, and recovering the values from the filtrate.

4. The process of recovering molybdenum from its vmolybdate ores and concentrates which comprises reducing said ore or concentrate to a suitable condition of fineness for further chemical treatment, mixing the pulverized material with Water and with sodium carbonate to form a pulp, heating the pulp at a temperature above 212 F.

i until a soluble molybdate is formed, filtering, neutralizing the filtrate and recovering values from the neutralized filtrate.

5. The process of recovering molybdenum from its molybdate ores and concentrates which comprises reducing saidore or concentrate to a suitable condition of fineness for further chemical treatment, mixing the pulverized material with Water and with a non-volatile alkaline metal compound, the aqueous solution of which is alkaline to form a pulp, heating the pulp at a temperature above 212 F. until a soluble molybdate is formed, filtering, neutralizing the filtrate, adding a soluble ferric salt of iron to the neutralized filtrate to precipitate a double oxid of iron and molybdenum, removing said precipitate and reducingit to ferro-molybdenum.

6. In a process of recovering molybdenum from ores or concentrates thereof, the step which comprises leaching the molybdenum-bearing material with a suitable solvent comprising an alkaline sodium compound in sufficient proportion to secure a commercially complete extraction of the molybdenum, as molybdate while leaving undissolved a substantial proportion of the impurities of the ore.

7. In aprocess of recovering molybdenum from ores or concentrates thereof, the step which comprises leaching the molybdenumbearing material With a sodium carbonate solution in sufficient proportion to secure a commercially complete extraction of the molybdenum, while leaving undiss'olved a substantial proportion of the impurities of the ore.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

EDWARD M. HAMILTON.

Witnesses:

H. E. Wnsr, S. E. WOODWORTH. 

